Classification and Structure
Three main chemical classes of calcium channel blockers are used in the management of angina:
- Phenylalkylamines (represented by verapamil).
- Dihydropyridines (nifedipine, amlodipine, etc.).
- Benzothiazepines (diltiazem).
These drugs selectively block voltage-gated L-type calcium channels, which open in response to cell membrane depolarization. The primary target for these medications is the α₁-subunit of the channel, which acts as the voltage-sensing module. These channels are located in cardiomyocytes and vascular smooth muscle cells of resistance vessels.
Organ Selectivity
Different classes of CCBs exhibit varying tissue affinities for the heart and the vascular bed:
- Phenylalkylamines demonstrate pronounced cardioselectivity, acting primarily on cardiac tissue.
- Dihydropyridines possess high vasoselectivity, affecting blood vessels predominantly.
- Benzothiazepines occupy an intermediate position, affecting both the myocardium and the vascular system.
These differences determine the pharmacological response profile and hemodynamic effects of each specific class.
Dihydropyridines in Hypertension
Selective class II calcium channel blockers are widely used as antihypertensive agents. These include dihydropyridine derivatives such as nifedipine, amlodipine, felodipine, nitrendipine, isradipine, and lacidipine.
Calcium ions are critical for maintaining normal vascular tone. During membrane depolarization of vascular smooth muscle cells, L-type calcium channels open, allowing an influx of ions into the cell and increasing cytoplasmic calcium concentration, which triggers muscle contraction.
By blocking these channels, dihydropyridines impair calcium entry, relax vascular smooth muscle, decrease total peripheral resistance (TPR), and lower blood pressure.
Clinical Priorities in Therapy
The overall pharmacological profile of the group is characterized by a combined antianginal effect. The drugs simultaneously decrease myocardial oxygen demand and increase myocardial oxygen supply.
When prescribing dihydropyridines in clinical practice, a strong preference is given to long-acting formulations. These specific dosage forms guarantee a stable antihypertensive effect and help minimize adverse hemodynamic reactions.